Jump to content
308AR.com Community
  • Visit Aero Precision
  • Visit Brownells
  • Visit EuroOptic
  • Visit Site
  • Visit Beachin Tactical
  • Visit Rainier Arms
  • Visit Ballistic Advantage
  • Visit Palmetto State Armory
  • Visit Cabelas
  • Visit Sportsmans Guide

Phantom30

Members
  • Content Count

    97
  • Joined

  • Last visited

About Phantom30

  • Rank
    0

Recent Profile Visitors

170 profile views
  1. don't know much about a 260 Rem other that the public SAAMI
  2. above "cold" should be "could" and "spherically" should be "specifically", too slow on edit again
  3. The one time test and data was sent to Hornady in July 2018. Never said break. The dents would probably have a minor effect on ballistics since the spin rate is so high and the mass of the plastic low. On the other hand where the tips were lead the deformation effected the mass distribution and dramatically demonstrated the effect. Granted those tips should not be used in an AR format but the effect changed concentricity and opened up accuracy. The point of the Lead tip test is to demonstrate that the forces encountered during chambering where significant. Copper OTM or HP although a much harder material still cold produce a flyer on occasion. Your vast experience with 260 Remington is not the same as the chambering issues with a Creedmoor. Recommending a Toolcraft BCG is a good thing but for a Creedmoor since it has been reported to have ejection and primer punch issues, the recommendation should include the high pressure 6.5 CM specific versions, single or dual ejector. In the velocity measurement chart it was noted that the post burn thru shot primers were all burred, on either brand of ammo used. This would indicate that the burn thru jetted the FP hole in the bolt face making it unsafe. The image of the primers fired using the new bolt installation shows a nice small strike pockets. Both ammo lots were tested with the new BCG, one fired hot lot ammo primer did show a slight ridge. No chronograph was allowed during this verification exercise so you couldn't attribute a velocity to that casing. Lessons learned here is that vendors advertise their BCGs will work in Creedmoor ARs, I am sure that's true but to be fully truthful the BCG should be the type spherically designed for the Creedmoor AR.
  4. Barrel parts is White Oak Armament (WOA) can't believe this thread has gone on this long with out somebody say you need to get your gas tubes there plus blocks etc. https://www.whiteoakarmament.com/shop/upper-parts-248/barrel-group.html I have found the in a 6.5CM you might consider the Toolcraft dual ejector 6.5CM specific BCG, it has the smaller FP diameter The ACC break is good have one on my 300WM and the interface to less noise works well.
  5. Thanks SS the bolt change recommendation solved the problems. Switched from the 308W Toolcraft single ejector NIB BCG to the Toolcraft 6.5CM small tip FP 0.065" instead of 0.077" plus dual ejector. Plus thoroughly clean chamber more often with 308W AR brushes and mop. All is now well, shooting sub-MOA with my cheapest parts I can find DIY built rifle.
  6. GR "That's a singular issue, with a singular user here, and singular use of the cheapest parts he can find to build a gun. That's all that is... " Interesting assessment thanks for the help. You really are near a desert border
  7. That rifle fired some of the round count in previous lots in the total S&B count. Not involved in the lot 16/78 count under consideration. The BCG in this rifle is a Toolcraft NiB, with standard 0.077" FP tip, single ejector. Barrel is a 22" bear creek Arsenal (BCA) SS straight fluted 1:8 twist, 6 grove 6.5 Creedmoor chamber with their standard barrel extension. The receivers are AP, gas system is WOA standard rifle length AR-10 gas tube with large match block. JP recoil eliminator break. Recoil system AP. The SAAMI standard nominal velocity for 140gr 6.5 CM is 2690 + 90 FPS, even the so called hot box was well within the manufactures standard. The COAL on the Defender rounds was 2.805, Hornady ELD 2.805, S&B FMJ was 2.740, SAAMI Mean average pressure limit is 62kpsi. The standards do not discriminate between bolt guns and gas guns so they should be equally capable of firing factory ammunition.
  8. The Davidson Defense bolt is in a KAK carrier in the 24" gas gun not involved here. Any switch in BCG's would have happened prior to the purchase of the 16/78 lot in question, so the round count stands.
  9. No the head spacing has not been verified or compared Yes probably next step now, is to get the tool craft Creedmoor bolt, as shooterrex and survival shop have recommended
  10. 392heminut The last three of my posts go together, the muzzle velocities are choreographed and the casings have a direct one to one correlation. willbird This thread is not about caliber to caliber performance but about the specific function of my 22" Creedmoor AR and the effects of ammunition. chambering and the BCG It has been purported that the culprit is the factory ammunition lot being more energetic than normal lots. In this case that has been shown to be relevant, but it still doesn't answer why this rifle has started to eat primers verses the bolt gun firing the same ammunition. Why does the bolt gun primers remain normal and the AR is leaving the primes raised and burred using multiple brands of ammo boxes shared between the two types of rifles. Why has this BCG started to fail to eject the last round in a stack? Has the primer burn thru effected the ejector, which by the way does appear scorched on the outer side.
  11. The evidence from the small samples above does show an increase in muzzle velocity between lots 11/10 and 16/78. However, the difference didn't cause punched primers in the bolt gun. All of the bolt gun primers felt smooth. The near same velocities in the AR all caused flowing primer strikes on two different brands of rounds and all post strike primers felt burred to the touch. Something other than ammunition lot muzzles velocities is happening here, which is the point in the origin of this thread.
  12. The primers for the above test shots
  13. Bolt gun, AR and ammo comparisons
  14. The picture below is the range record for the "Hot Box" event. The lot number is visible on the lid as previously reported. The raised non-punched rounds are also displayed for comparison on the 1st entry on this thread. I can provide bolt face photos if desired. They do have a rolled lip pin strike that sticks up slightly. The round count of over 200 applies to this specific barrel, many others have been fired in other rifles.
×
×
  • Create New...